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```Introduction to Electronics: The Diode

Make] Projects

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build, hack, tweak, share, discover,-

Introduction to Electronics: The

Diode

Written By: KRA5H

TOOLS:

Snap Circuits Extreme 750 set (1)

PARTS:

Base Grid (11" x 7.7") # 6SC BG (1)
Battery Holder (2-AA^ # 6SC B1 (1)
6V Lamp Socket (With Bulb) # 6SC L2

in

Slide Switch # 6SC S1 (1)
Conductor with 2-snaps # 6SC 02 (4)
Conductor with 3-snaps # 6SC 03 (1)
Diode 1N4001 #6SCD3(1)
RedLED#6SCD1 (1)
100 ohm Resistor # 6SC R1 (1)

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Page 1 of 9

Introduction to Electronics: The Diode

Step 1 — Introduction to Electronics: The Diode

• According to Wikipedia , "The most
common function of a diode is to
allow an electric current to pass in
one direction (called the diode's
forward direction), while blocking
current in the opposite direction
(the reverse direction). Thus, the
diode can be viewed as an
electronic version of a check
valve."

Step 2

Surface of water

• What is a check valve? You can
think of it like a ping pong ball cage
snorkel.

• When the ping pong ball cage is
above the surface of the water, the
ping pong ball is at the bottom of
the cage and you can breathe
through the snorkel. As the cage
moves below the surface of the
water, the ping pong ball floats up
until it blocks the opening of the
snorkel blocking any water from
getting into the snorkel.

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Page 2 of 9

Introduction to Electronics: The Diode

Step 3

• The diode has a number of
applications in electronic circuits.
One application you may be
familiar with is a rectifier. A
rectifier converts alternating
current (AC) to direct current (DC).
Alternating current periodically
changes direction while direct
current only flows in one direction.

• To use a diving analogy, imagine a
scuba diver. Since scuba divers
carry their air with them they can
are above water or underwater.
You can imagine a scuba diver
surfacing and diving repeatedly and
the path the diver traces forms a
sine wave.

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Page 3 of 9

Introduction to Electronics: The Diode

Step 4

• The sine wave is what alternating
current looks like. At the crest, or
top of the wave you might measure
+5 volts and at the trough, or
bottom of the wave you might
measure -5 volts. At the line
through the middle you would
measure volts.

Step 5

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Surface of water

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• Let's say we wanted to use a diode as a rectifier to convert alternating current to direct
current.

• Now imagine our snorkeler surfacing and diving. While the ping pong ball cage on the
snorkel is above the water the snorkeler can take a breath of air.

• When the cage sinks below the water the ping pong ball blocks the water from getting into
the snorkel and the snorkeler has to hold his or her breath until surfacing again to exhale
and take another breath.

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Page 4 of 9

Introduction to Electronics: The Diode

Step 6

• Like the ping pong ball acts as a
check valve to prevent water from
getting into the snorkel, the diode
acts as a check valve to block
current from flowing in the reverse
direction.

• The diagram is what the voltage
will look like when the alternating
current is converted to direct
current.

• You would measure from volts to
+5 volts then back to volts. You
wouldn't be able to measure the
voltage in the reverse direction
from volts to -5 volts because it
is being blocked by the diode.
When the alternating current cycles
back to volts you would then be
able to measure the voltage from
volts to +5 volts and then back to
volts.

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Page 5 of 9

Introduction to Electronics: The Diode

Step 7

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• Now we can see what happens when we reverse the diode. Build the circuit shown with the
diode in the reverse direction. The photos show the step-by-step build. When you're done
building the circuit, slide the switch (S1) from the off position to the on position.

Wei I... nothing happens.

• In a DC (direct current) circuit, the electricity flows in one direction.

• When you switch the circuit on you can think of it as current flowing from the positive side
of the battery (marked with a "+" sign) to ground (marked with a "-" sign) and you can think
of the flow of current as kinetic energy that can be used to do useful work such as light up
an incandescent bulb.

• So, when you switch the circuit on, why doesn't the light bulb light up? Because the diode
is blocking the flow of electrcity like the ping pong ball on the snorkel blocking the water
from getting in.

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Page 6 of 9

Introduction to Electronics: The Diode

Step 8

• Switch the circuit off and change the diode from the reverse direction to the forward
direction. Then switch the circuit on and the light bulb lights up.

• Now the diode is no longer blocking the flow of electricity and current can flow from the
positive (+) terminal on the battery through the circuit to the ground (-) terminal on the
battery.

Step 9

• This is the electronic symbol for
the diode so that you will be able to
recognize it on an electronic
schematic.

• When a positive voltage is applied
to the terminal on the left and a
negative voltage to the terminal on
the right, the diode is "forward
biased" and current wiill flow
through it.

• If the polarity is reversed, the diode
is "reverse biased" and no current
will flow.

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Page 7 of 9

Introduction to Electronics: The Diode

Step 10

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• Now let's take a look at the Light Emitting Diode (LED).

• The light emitting diode functions much the same as an ordinary diode, but also lights up
when enough current is flowing through it in the forward direction (forward-biased). LEDs
are often used in electronic devices to indicate that the device is switched on, but they can
serve many practical purposes.

• Build the circuit shown. The photos demonstrate the step-by-step build.

• When you switch the circuit on. ..again, nothing happens. Why doesn't the light LED light
up? Because the LED is reversed and blocking the flow of electrcity.

Step 11

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• Switch the circuit off and turn the LED around.

• Now you can switch the circuit on and with the LED in the forward-biased direction, it lights
up.

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Page 8 of 9

Introduction to Electronics: The Diode

Step 12

"i.

• This is the electronic symbol for
the LED so that you will be able to
recognize it on an electronic
schematic.

This document was last generated on 201 2-1 0-30 07:21 :59 PM.